Scottish saltmarsh, sea-level rise, and the potential for managed realignment to deliver blue carbon gains

Vegetated coastlines, including seagrass, mangroves, and salt marshes, are valued for their capacity to sequester and store large amounts of organic carbon in their soils. The importance of ‘blue carbon’ habitats in mitigating against climate change is now widely recognised, especially given that blue carbon accumulation rates are expected to increase in response to sea-level rise, temperature increase, and precipitation change. However, coastal habitats are degrading globally, raising fears that blue carbon habitats could largely disappear by the end of this century unless significant protection and restoration efforts are enacted. Scotland’s saltmarshes are currently estimated to cover an area of 58.4 km2, which represents around 13% of the UK total. The Scottish Government has recognised their importance in the Climate Change Plan Update, and the inclusion of saltmarsh in the national greenhouse gas inventory is being progressed by the UK Department of Business, Energy and Industrial Strategy (BEIS), following recent recommendations to do so by the UK Climate Change Committee. Such inclusion would allow saltmarsh restoration to contribute to meeting our emissions reduction targets. This study assesses the potential for managed realignment of Scotland’s coastline to create suitable areas for saltmarsh habitats within the intertidal environment specifically for blue carbon benefits. It examines existing evidence and uses modelling to explore the potential for additional blue carbon sequestration. It also explores the likely effects from future sea-level changes on these newly created saltmarsh habitats and their associated soil carbon stocks. We recognise there are other approaches to restoration, but they will not be addressed here.